As an image forming apparatus such as a printer, facsimile, copier, plotter, or a multifunctional peripheral including the printer, facsimile, copier, and the plotter, an inkjet recording apparatus is known. The inkjet recording apparatus is a liquid jet recording type image forming apparatus using a recording head configured to jet ink liquid drops. In this liquid jet recording type image forming apparatus, the ink liquid drops are jetted from the recording head onto a conveyed sheet so that image forming such as recording or printing is performed.
Hereinafter, the “image forming apparatus” means an apparatus configured to jet liquid onto a medium such as a paper, thread, fiber, leather, hides, metal, plastic, glass, wood, or ceramic so that images are formed. The image forming apparatus includes a mere liquid jetting apparatus. In addition, “image forming” means not only providing an image of characters, figures, or the like on the medium but also providing an image such as a pattern having no meaning on the medium. “Image forming” includes adherence of the liquid drops onto the medium.
Furthermore, “ink” is not limited to the recording liquid or the ink and any liquid that is a fluid when being jetted can be applied to the liquid such as fixing liquid. In addition, the “ink” includes a liquid whereby the image forming can be performed, such as a resist or DNA testing material.
In addition, “sheet” is not limited to a paper but includes an OHP sheet or leather. In other words, the sheet means a subject where the ink drops are adhered. The sheet includes a recorded medium, a recording medium, a recording paper, and a recording sheet.
As such an image forming apparatus (hereinafter “ink jet recording apparatus”), the following apparatuses have been known. In one apparatus, a sub-tank (buffer tank) configured to supply ink to a recording head is mounted on a carriage; a main ink cartridge (main tank) is provided at an apparatus main body; and the ink is supplied and supplemented from the main ink cartridge of the apparatus main body to the sub-tank. In another apparatus, an ink cartridge which is a liquid container exchangeable with a recording head is provided.
As described in Japanese Laid-Open Patent Application Publication No. 2003-1846 and Japanese Laid-Open Patent Application Publication No. 2003-89217, a sub-tank having an air opening valve configured to open an inside to the atmosphere has been suggested. In this suggested example, the air opening valve includes an opening part, a seal part, a spring mechanism, a pressing mechanism part, and a filter. The opening part corresponding to an air opening part is provided on an upper surface of the sub-tank. The seal part is configured to seal the opening part. The spring mechanism part presses the seal part to the opening part. The pressing mechanism part is configured to press the seal part into a sub-tank. The filter is provided outside the opening part. The air opening valve normally blocks an inside of the sub-tank from the atmosphere and is opened by the pressing mechanism part. The example where the filter is provided has been suggested in Japanese Laid-Open Patent Application Publication No. 2003-53985 and Japanese Patent 3087535.
However, in a case where the filter is simply provided at the air side opening of an air communicating path like the above-mentioned related art, foreign particles which cannot be caught by a filter member may enter the air opening path as they are so that of sealability of the valve member may be degraded. As a result of this, sealability of the liquid container may be degraded so that the air enters the container. Hence, it may not be possible to supply the ink stably.